The present invention relates generally to the storage of compressed data to a storage device.
For purposes of this application, the phrase xe2x80x9cmopy printerxe2x80x9d refers to any laser printer (e.g., network printer, copier or facsimile machine) that can print one or more copies of a document from compressed video data stored in a local disk drive unit. The actual operation of printing from the hard disk drive is referred to herein as a xe2x80x9cdisk-print operationxe2x80x9d. In addition, the rate at which the compressed video data can be read from the disk drive is referred to herein as the xe2x80x9cdisk output ratexe2x80x9d.
Typically, a mopy printer performs a disk-print operation by use of a data pipeline. The data pipeline includes at least a disk drive unit, a data decompressor and a print engine. During a disk-print operation, compressed video data stored in the disk drive unit is transmitted by the disk drive unit to the input buffer of the decompressor. As the compressed data is received, the decompressor operates to decompress it and to transmit the resulting decompressed video data to the input buffer of the print engine. As the print engine receives the decompressed video data, the print engine prints the document.
Importantly, during a disk-print operation it is often desirable for the disk drive unit in the data pipeline to have a disk output rate above some minimum rate. This minimum rate is referred to herein as the xe2x80x9cminimum disk output ratexe2x80x9d. If the disk drive unit in the pipeline is not able to transmit compressed video data at the minimum disk output rate, then the data pipeline is not able to process the data at an adequate rate (i.e., the pipeline is not able to run at xe2x80x9cfull speedxe2x80x9d). This can result in reduced printing speed or in causing a print underrun condition. In the case of a print underrun condition, video data is not transmitted to the print engine at the required rate and the document currently being printed is not properly printed.
In the prior art, the actual disk output rate during a disk-print operation is often unpredictable and may not be above the minimum disk output rate required for the pipeline to run at full speed. As indicated above, this can result in an undesirable reduction of printing speed or the occurrence of a print underrun condition or both.
Accordingly, there is a need for a way to ensure that a disk drive unit in a mopy printer has an disk output rate above the minimum disk output rate during a disk-print operation.
The present invention is directed to satisfying the need to ensure that a storage device, such as a disk drive unit in a mopy printer, is able to transmit compressed data at a minimum disk output rate. The minimum disk output rate being a function of the compression ratio of the compressed data being transmitted.
In one embodiment of the invention, apparatus is provided for writing compressed data to a storage device. The storage device having a plurality of storage areas each having a characteristic transfer rate. The storage device has at least a minimum disk output rate if the compressed data is stored in a storage area having a characteristic transfer rate above a minimum transfer rate. The minimum transfer rate being a function of the compression ratio of the compressed data. The apparatus includes means for using the compression ratio to identify at least one storage area from the plurality of storage areas. The at least one storage area has a characteristic transfer rate above the minimum transfer rate. The apparatus further includes means for writing the compressed data to the at least one storage area.
The storage device may be, for example, be a disk drive unit that includes a disk storage media. The disk storage media may include a set of tracks each having a characteristic transfer rate above the minimum transfer rate. The at least one storage area identified by the identifying means includes a track from the set having the lowest characteristic transfer rate.
In another embodiment, a computing system is provided comprising a storage device and a controller coupled to the storage device. The storage device includes a plurality of storage areas for storing and transmitting compressed data. The controller is operable to identify at least one of the storage areas to receive the compressed data based upon a compression ratio of the compressed data and is further operable to write the compressed data to the at least one storage area. The storage device having at least a minimum disk output rate when transferring data from the at least one storage area and the minimum disk output rate being a function of a compression ratio of the compressed data. The compressed data may be compressed video data and the computing system may be a mopy printer.
In yet another embodiment a method of writing a compressed data to a storage device is provided. The storage device having a plurality of storage areas and having at least a minimum disk output rate when transferring data from at least one of the plurality of storage areas and wherein the minimum disk output rate being a function of a compression ratio of the compressed data. The method includes identifying the at least one storage area from said plurality of storage areas based upon said compression ratio, and writing the compressed data to said at least one storage area. The storage device may include a disk storage media and the at least one storage areas may include a track on the at least one disk storage media. The disk storage media may include a plurality of tracks each of which having a characteristic transfer rate and wherein the storage device having at least a minimum disk output rate when transferring data from each of said plurality of tracks and wherein the track being a track from said plurality of tracks having the lowest characteristic transfer rate.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.